1) Field of the Invention
This invention relates generally to mine roof support trusses and, more particularly, to apparatus for installing mine roof support trusses.
2) Description of the Prior Art
Truss-type mine roof supports are well-known in the art of supporting the roof of an underground passageway, such as a passage. A basic truss system includes one or more rods extending horizontally across the width of the mine passage adjacent to the roof with the ends connected to anchor bolts which extend at an angle adjacent the ribs of the passageway into the rock strata or a solid pillar. The rods are tensioned and the resultant force produces an uplifting effect to the unsupported rock material immediately above the passageway.
With this arrangement, a truss system shifts the weight of the rock strata from over the mined out passageway back onto the pillars. Conventionally, holes are drilled into the mine roof at a 45.degree. angle from the horizontal adjacent to the mine rib so that the holes extend into the supported rock structure of a pillar. To insure adequate anchorage over the pillar at the ribline, the bolts often extend above the supported structure of the pillar.
Once the angle holes are drilled into the strata over the pillars at the ribline, anchor bolts are inserted in the drilled holes and are secured in place using mechanical expansion shell assemblies in combination with resin. This arrangement insures adequate anchorage over the ribline for the bolts. Before the bolts are inserted in the drill holes, truss shoes or bearing blocks are positioned on the bolt at the emergent end of the bolt from the hole. As the bolts are securely anchored in the bore holes, the bearing surfaces of the truss shoes or bearing blocks are compressed into engagement with the mine roof.
Once the truss shoes or bearing blocks are securely positioned at the mine roof adjacent the ribs, the horizontal truss members are assembled and connected to the truss shoes. The truss members are tightened to a preselected torque to exert tension on the truss members which produces the resulting uplifting force applied to the roof above the mine passageway.
A wide variety of truss hardware is commercially available to form a truss system between the anchored angle bolts. The truss hardware is connected under tension to the truss shoes or bearing blocks that are held tightly against the mine roof by the anchored angle bolts.
Some of the more popular type of truss systems are disclosed in U.S. Pat. Nos. 4,596,496; 5,026,217 and 5,302,056. These truss systems include truss shoes having an arrangement that receives the closed or arcuate end of a U-bolt. This facilitates ease of assembly and disassembly of the U-bolt on the truss shoe without requiring the U-bolt to be threadedly connected to the shoe or extended through an opening in the shoe. The U-bolt is not securely connected to the truss shoe until it is placed in tension. When the connected truss members are tensioned, the U-bolts are drawn together, typically by a torquing rod or bolt, and securely retained on the truss shoes.
As presently practiced the tensioning of the torquing rods is a tedious and dangerous process, which presently is done by a miner. The miner either uses a hand-operated wrench or a hand-held wrench driven by a hydraulic pump (such as provided on a standard mine bolt bolting machine) to tension the torquing bolts. The miner must then position himself or herself directly under the U-bolt adjacent to the torquing rod nut and engages the wrench with either the head or the nut of the torquing rod, and then tensions the rod. As previously stated, this is a tedious and dangerous job. Further, if the miner is hand-tightening the torquing rods, then the miner experiences fatigue. This also occurs with a hydraulically driven wrench, since they are quite heavy and must be held and positioned by the miner during the tensioning of the torquing rods. Thus, the installation of the truss systems can become more expensive throughout a shift, since the miner will typically take longer to tension an individual torquing rod as the shift progresses.
Therefore, it is an object of our invention to overcome the expense, tedium and dangerous aspects of installing and tensioning the truss-type mine roof bolt systems.